Most of our nearest relatives are, like us, social beings, forcing them to find ways to cooperate. Chimpanzees are no exception, and a study of them performing group tasks has found strong parallels with the way humans combine, suggesting this behavior has deep evolutionary roots.
To test chimpanzee cooperation, a team led by famed primate researcher Professor Frans de Waal of the Yerkes National Primate Research Center challenged a group of 11 adult chimpanzees to cooperate for a reward. One chimp had to remove a barrier while another pulled in a plate carrying a piece of fruit. No individual could manage both roles on their own. Subsequently, the challenge was altered to require a third participant.
The scenario was obviously different from one the apes would have been familiar with, and they took some time to understand how it worked. Nevertheless, they managed well. In Proceedings of the National Academy of Sciences, the team reports that some chimps tried to “freeload” by letting others do the work and then stealing the food themselves, or not sharing with their co-worker. However, effective mechanisms developed to punish this, and over the thousands of successful fruit captures, cooperative acts outnumbered those where one chimpanzee cheated by five to one.
After a piece of fruit had been delivered the plate would be immediately refilled, and this went on for an hour at a time. Consequently, fights that interfered with this would eat into the total amount of fruit that could be captured in the space of an hour. This seldom happened. In the space of 94 test sessions, 3,656 pieces of fruit were captured, despite the fact that the chimpanzees were relatively new to each other and still in competition to establish social rank.
Past laboratory experiments on chimpanzees have produced more competition than cooperation, but the authors argue this reflected experimental design. “We find that chimpanzees in these restricted settings may not have had adequate opportunities to use appropriate enforcement strategies,” they write. Without any means to punish cheaters, it is unsurprising that freeloading came to dominate over joint action.
In the experiment, however, individuals had several ways to deal with those who wanted to eat without doing their share of work. These ranged from vocalizing their dissatisfaction with a mix of whimpering and screaming, through to hitting or biting the cheat. In 8 percent of cases, a third ape intervened, usually to punish the freeloading chimp. However, possibly the most effective mechanism was partner choice. Once they worked out that acquiring fruit required teamwork, individuals approached others to be their partners, and freeloaders found themselves shunned.
Although there was an initial rise in competition as participants jockeyed for opportunities to grab the fruit, they soon decided cooperation worked better; for the second half of the experiment cheating virtually disappeared.
The results challenge claims that human cooperation is a “huge anomaly” in the animal kingdom. Evidence keeps emerging of just how common cooperation is within, and sometimes between, species for the simple reason that it works.
